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April 17, 2024, 08:55 |
Turbulence for natural external convection
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#1 |
New Member
Gustavo
Join Date: Mar 2024
Location: Brazil
Posts: 7
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Hello. I'm trying to set up a case of natural external convection where a fluid flows around a hot cylinder due only to temperature differences. I have done laminar tests and it worked fine with great results.
Now I wanna add turbulence (by modifying Rayleigh parameters) but I can't figure out how to set up the initial BCs for turbulence. My professor told me to use k-omega-SST model, but I'm not able to judge the best BCs for the files of k/omega/alphat/nut. In my case the fluid is initially quiescent (zero velocity) and starts moving only due to the natural convection, but because of this I can't calculate what the initial values for k/omega should be, since the fluid isn't moving at the beggining. Also, my mesh consists of: inlet/outlet = patches superiorPlane/inferiorPlane = symmetryPlane cylinderWall = wall frontAndBack = empty I'm a begginer at OpenFOAM, so I'm sorry for stupid mistakes. No fvModels present No fvConstraints present #0 Foam::error:rintStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 ? in "/lib/x86_64-linux-gnu/libc.so.6" #3 Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:? #4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam:perator/<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<doub le, Foam::fvPatchField, Foam::volMesh> > const&, Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&) at ??:? #5 Foam::fluidThermo::nu() const at ??:? #6 Foam::RASModel<Foam::compressibleMomentumTransport Model>::nu() const at ??:? #7 Foam::kOmegaSST<Foam::eddyViscosity<Foam::RASModel <Foam::compressibleMomentumTransportModel> >, Foam::compressibleMomentumTransportModel>::F2() const at ??:? #8 Foam::kOmegaSST<Foam::eddyViscosity<Foam::RASModel <Foam::compressibleMomentumTransportModel> >, Foam::compressibleMomentumTransportModel>::F23() const at ??:? #9 Foam::kOmegaSST<Foam::eddyViscosity<Foam::RASModel <Foam::compressibleMomentumTransportModel> >, Foam::compressibleMomentumTransportModel>::correct Nut() at ??:? #10 ? in "/home/workstation1/OpenFOAM-10/OpenFOAM-10/platforms/linux64GccDPInt32Opt/bin/buoyantFoam" #11 __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #12 ? in "/home/workstation1/OpenFOAM-10/OpenFOAM-10/platforms/linux64GccDPInt32Opt/bin/buoyantFoam" Floating point exception (core dumped) Last edited by gushrqcosta; April 17, 2024 at 11:01. |
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April 17, 2024, 11:40 |
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#2 |
Senior Member
Join Date: Dec 2021
Posts: 241
Rep Power: 5 |
Hey,
It looks like a division by 0 occured somewhere! Try to avoir 0 values in your turbulent boundary conditions (you can use 1e-8 for instance) and in your fluid properties. Concerning initial values for turbulence, I guess you could estimate the max velocity reached once your convective pattern is established (a few m/s?) and get approximative values for k and omega. Initial values are just that, for the initial steps of the simulation. The turbulent quantities should converge towards realistic values afterwars. |
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buoyantpimplefoam, komegasst, natural convection, turbulence |
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